A carbon black reactor comprises three zones. The first zone is a combustion zone in which air and fuel are burned to produce highly heated gases which travel to a second zone, the reaction zone. In the second zone, a hydrocarbon feedstock such as oil is injected into the highly heated gases and, thus, is partially burned and partially "cracked" to produce carbon black. The highly heated gases with the carbon black entrained therein is passed to the third zone, the quenching zone. In the third zone, the gases and carbon black are quenched with water and then passed to filtering equipment for separation of the carbon black from waste gases and from water vapor.
The carbon black produced by this process is used in a variety of ways. For example, approximately ninety percent of the carbon black produced is utilized in the production of automobile tires, approximately six to seven percent is utilized in rubber moldings and similar products, and the remainder is used primarily in pigments and in inks.
A fine particle size carbon black generally is desirable since such particles have an extremely high surface area which may range from five square meters per gram of carbon black to two hundred fifty square meters per gram of carbon black.
Several methods exist for measuring the surface area of the carbon black. One of the most frequently used methods is the iodine adsorption test in which the amount of iodine adsorped by the carbon black is measured. In this test, the more iodine absorbed, the greater the surface area. This test generally can be successfully completed and results obtained within fifteen minutes. Another test similar to the iodine adsorption test is the nitrogen adsorption test, but it generally requires at least one hour to obtain results.
These tests, and specifically, the iodine adsorption test, are run during production to measure the surface area of the carbon black being produced. Since the iodine adsorption test is capable of being run much more quickly, it is the preferred test because it allows the production process to be readily adjusted so as to produce carbon black within certain parameters, for example, such as a given particle size. The size of carbon black is very important because it may dictate certain performance characteristics of products in which it is used. Discrete particles in each grade of carbon black vary in size when measured by microscopic or adsorption means. Accordingly, the particle size is expressed as an average size of the particles measured. Iodine adsorption tests, such as ASTM D 1510-88B are needed to determine whether the proper size of carbon black is being produced. Producers of carbon black are paying increased attention to particle size control because more buyers of carbon black are requiring a product which is more uniform in size. In some instances, the product must not vary more than plus or minus three iodine adsorption units rather than five or ten, as in the past. Thus, the control of the process by which carbon black is made has become very important.
In U.S. Pat. No. 3,993,447, Buss et al. disclose an apparatus and method for the production of carbon black wherein the uniformity of the carbon black is maintained by regulating the flow of fuel to the combustion zone in response to a signal representative of the combustion zone temperature. The flow of fuel to the combustion zone can be regulated in response to a signal representative of the rate of combustion heat released by the fuel entering the combustion zone. U.S. Pat. No. 4,080,434 to Buss et al. is a division of an earlier filed application which matured into U.S. Pat. No. 3,993,447.
In U.S. Pat. No. 4,206,192, Austin discloses a method for the production of carbon black in a carbon black reactor having at least one combustion zone opening into a reaction zone. Austin controls the quench fluid flow rate into the combustion zone in order to control the temperature of the combustion gases. This temperature control is desired in order to protect the refractory lining of the combustion zone. U.S. Pat. No. 4,315,894 to Austin is a division of an earlier filed application which matured into U.S. Pat. No. 4,206,192.
In U.S. Pat. No. 4,302,423, Cheng et al. disclose an apparatus and method for producing carbon black in a carbon black reactor. Cheng et al. utilize a control means to produce a signal representative of the rate of heat transfer in the indirect heat exchange means such that when the heat transfer rate falls below a predetermined level, the control means closes a valve in the feed hydrocarbon input line to terminate flow of feed hydrocarbon to the reactor. Cheng et al. provide a method for producing carbon black which can be operated substantially continuously without the need of completely terminating operation for cleaning of an indirect heat exchanger to maintain the heat exchange rate in a desired range, that is, to minimize carbon black buildup in an indirect heat exchanger.